Wonderleaf
A Wonderleaf question
A five-minute wonder
Somewhere tonight the sky is on fire, and nobody lit it. The answer starts ninety-three million miles away.
On some winter nights, near the top of the world, the sky begins to ripple. Green curtains sway from star to star. Pink ribbons flicker along their hems.
Nobody is up there holding a lantern. So where does the light come from? The story starts far, far away — with our Sun.
Step one · The Sun
It seethes, and it spits. Every second of every day it throws tiny pieces of itself out into space — far too small to see, far too many to count. Scientists call it the solar wind, though it is nothing like wind here: a spray of sparks, blowing in every direction at once.
Step two · The crossing
Look how small we are in that picture. The sparks have ninety-three million miles of cold dark to cross, and it takes them about two days. While they travel, you eat breakfast. You go to school. You fall asleep.
Step three · Arrival
The travellers arrive above a dark, sleeping world. And here they run into something nobody can see — something our planet has been wearing the whole time.
Not a wall — a slide.
Earth is a giant magnet. All around it stretch invisible magnet-lines, looping out of the top of the world and back in at the bottom, like the drawing beside you.
When the Sun's sparks arrive, most swerve wide around us. But some are caught — and the lines slide them along, like beads on a curved wire.
Every line gathers at the same two places: the poles. So that is where the sparks get poured — which is why the lights love the far north and the far south.
Step five · The crash that glows
Sixty to a hundred and fifty miles above the snow, the sparks finally hit something: air.
60–150 miles up — far higher than any airplane flies
the air up here is thin and quiet: oxygen and nitrogen
every single crash makes one tiny flash of light
When a spark from the Sun crashes into a bit of air, that bit of air jolts awake — then settles down again by letting go of a tiny flash of light.
One crash, one flash, far too small to see. But the Sun sends billions of sparks. Billions of crashes, billions of flashes — and together they become a glowing curtain taller than a hundred mountains.
The sky is not being lit. It is being hit.
Say it tonight. It is the whole secret in seven words.
From far away, it is a green sky.This close, it is brushstrokes of oxygen light.
Most of the show is oxygen, struck in the middle of the aurora's home, glowing green — the colour you will nearly always see first. If the curtains look like green silk, that is oxygen singing.
Lower down, the sparks reach nitrogen. Nitrogen answers in pink, so pink gathers along the bottom edges — a ruffle at the hem of the curtain.
And at the very top, where the air is barely there at all, oxygen glows a deep, slow red. It is rare. Catching it is a lucky night indeed.
The Sun throws off tiny charged pieces of itself.
They fly through space for about two days.
Earth's magnet catches them and slides them to the poles.
They crash into the air — and the air glows green, pink, and red.
That's the whole secret. Tell it at dinner.
Put it all together —
…and you get one glowing sky. That is what causes the northern lights.
Somewhere near the top of the world, it is happening right now.
Watercolour scenes, straight answers, about three minutes cover to cover.
Open the picture bookMore wonders for curious heads
One more wonder: Why is space so dark?
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